Composite polymeric film form materials are well known in the plastics art. It is well known to make such a composite of a construction such that it is usable for applying releasably secured film form material thereto, such as peelable labels.
In the known construction, a base liner of suitable film form material has a release coating applied to at least one surface thereof. A tacky adhesive material is applied to at least one surface of a face stock, and the face stock is releasably adhered to the base liner by contact of this tacky adhesive with the release coating.
The release coating is a material which adheres well to the base liner but has the property of only lightly holding, and therefore easily releasing, the adhesive coated face stock film form material which is applied thereover. This structure allows the production of peelable labels and the like in a most efficient fashion.
In this sort of composite film form material, it is conventional to make the release coating out of an electron beam curable composition comprising a silicone resin to which crosslinkable groups, such as acrylic residues, have been appended. The silicone portion of the composition acts as a release agent, and the acrylic groups act to crosslink the release coating composition together and to bond this composition to the base liner surface.
It has been found that, although this composite structure works well and constitutes a commercially available material, there are some things about this structure which perform less than satisfactorily. It has been found that, when the composite of the release coating and the base liner is made as an extended length film, and it is rolled up upon itself for storage, subject to later use by having face stock suitably applied thereto, portions of the release coating composition apparently do not crosslink when subjected to the electron beam curing process. It is not known if these portions of the compositions do not have acrylic substituents, or if they do have such substituents and just have not reacted sufficiently to be well bound into the release sheet.
In any case, whatever is the reason, these more mobile portions of the release coating composition, principally those portions which are on the exposed surface of the release coating, called in the industry "loose juice", tend not to remain in the release coating composition layer. Upon the composite base liner and release coating being rolled up for storage or shipping, these portions come loose and transfer to the other side of the base liner; that is the back side of the base liner which is in contact with the release coating when the composite is rolled up. Upon transfer of this material to the back side of the base liner, it interferes with the later printing of indicia on the back side of the composite film.
Further, when the composite film material is unrolled, and a face stock is adhered over the release coating, it is conventional practice to once again roll up this new composite, of base liner, release coating, and face stock, for storage and transportation. Just as some of the loose juice tended to transfer from the release coating to the back of the base liner when the original composite was rolled up, some of the loose juice which is on the back of the base liner then tends to retransfer to the top of the face stock when this composite is rolled up. In this location, the transferred loose juice interferes with the adhesion of inked indicia sought to be printed on the top of the face stock.
Still further, the presence of unbonded silicone moieties which exist in the release coating tends to be detrimental to this product even if they do not transfer to the back of the base liner. Even if some of this loose juice transfers to the back of the base liner, still more of it stays in the release coating. At least some of the loose juice which remains in the release coating tends to migrate to the tacky adhesive on the face stock and reduces or eliminates its tackiness. The peelable face stock is necessarily tacky in this product or it will not adhere to another surface after it has been peeled from the base liner. If the tackiness of the adhesive is reduced or eliminated, the face stock cannot be used for its intended purpose.